Can someone post a photo of the square plate that mounts to the jar lid? Does it look like the attached photo? If so, what purpose does the large center hole serve? What kept water out of the cylinder?

That looks correct I thought the conduit box mounted there

My pump did have the junction box mounted there, but there was no hole on the center. The square metal plate on my pump is aluminum. The four bonnet mounting bolts are carriage bolts, probably not original, but they work.

It seems like rain water could enter the large center hole and go directly into the cylinder. There has be be some type of seal between the jar lid and the square plate.

There must be someone that has photos of a 600 series Tokheim visible above the jar lid.

Here is a top part of a 620 I did a couple years ago. Some of the parts are from Ron S. and others from Home Depot.
A mounted globe on the bonnet would cover that hole but so does the juncture box.

On the pic you posted the two small holes hold a bracket that the conduit box sits on but mine had no big hole in the center

Here is a picture of mine. It does not have the big hole either. Richard

Richard Is that the way tne piece is supposed to be I thought the grey piece is up side down in your pic
Bill

It is upside down. I had it stored on a shelf so I put it that way so it would lay flat. The bonnet was on top of it. Richard

Don’t know if this will help or not, it’s off a 620 and appears to be all original.

That is what I remember as being correct

Thank you huskybob. That is probably the same as the 660 plate. I am missing the deflector cup and the vent.

Can you measure the stud total length and the length of threaded part of the stud? Someone used carriage bolts as studs on my pump plate. It works, but looks bad.

Your photo also confirms the center support bracket for the junction box. I wasn't sure if that was original on my pump plate.

Thank you huskybob.